Very high frequency electron discharge tubes



1956 H. G. BRUUNING 2,730,650

VERY HIGH FREQUENCY ELECTRON DISCHARGE TUBES Filed Feb. 5, 1952 INVENTOR Hugo Georg Bruijning By %.(WW

Agent VERY HEGH FREQUENCY ELECTRUN DISCHARGE TUBES Hugo Georg Bruijning, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee I Application February 5, 1952, Serial No. 270,022 Claims priority, application Netherlands March 29, 1951 2 Claims. c1. 315-5) The invention relates to devices for very high radio frequencies, comprising an electric discharge tube, in which an electron beam modulated in intensity by means of the control-grid moves towards two high-potential, annular electrodes arranged after one another, a cavity resonator being'arranged to surround this tube externally between said limitation.

According to the invention a device for very high radio frequencies, comprising an electric discharge tube, in

which an electron beam modulated in intensity with the use of a control-grid moves towards two high-potential,

annular electrodes arranged after one another, a cavity resonator being arranged to surround the tube externally between these annular electrodes, the resonator having a slit round about the tube and having a natural frequency which isequal to the frequency of the intensity modulation,'is characterized in that the insulating tube wall between the first high-potential electrode and the rear side of the slit in the cavity resonator is shaped in such a form that this wall is struck by electrons throughout its surface.

Thus, a stable operation of the tube is obtained, which may be ascribed to the positive charges of this wall owing to secondary emission. It is in fact necessary for the whole Wall betwen the two said points to be struck by electrons, since otherwise the intensity modulation of the beam itself or the potential variations of the electrodes might lead to an incessant variation of the border between the wall part struck by electrons and that which is not struck, from which instability arises. If a very high beam intensity and only comparatively weak concentration means are used, the aforesaid conditions may be readily fulfilled, if the tube diameter is not too large.

United States Patent 0 ice A suitable form of a tube for use in the device according to the invention is one in which the tube diameter after the first annular electrode is reduced to such an extent that the internal diameter is slightly smaller than that of the preceding annular electrode, the diameter becoming gradually larger towards the second annular electrode.

In order that the invention may be readily carried into elfect, an example will now be described in detail with reference to the single figure of the accompanying drawing, which is a longitudinal sectional view of a tube for use in a device according to the invention.

Referring to the figure, 1 designates a discharge tube made of quartz, comprising a cathode 2, a control-grid 3 and a collecting electrode 4; 5 and 6 designate annular electrodes and immediately after the first annular electrode the tube wall is constricted at 7, after Which it gradually widens towards the ring 6. A resonator is shown diagrammatically and designated by 8.

What I claim is:

1. An electron discharge system for very high frequencies comprising an electron discharge tube including an envelope, a cathode, a control grid, first and second high potential annular electrodes, and a collecting electrode arranged in that order in the envelope, said first annular electrode having a given internal diameter, a cavity resonator surrounding said envelope between said annular electrodes and having an annular gap facing said envelope, said envelope having a wall portion betweensaid first annular electrode and the side of said gap remote from said first annular electrode having a reentrant portion whose internal diameter is smaller than the internal diameter of said first annular electrode and tapers outwardly toward the second annular electrode, whereby the wall portion is struck throughout its surface by electrons emitted by said cathode.

2. An electron discharge tube for use in systems for very high frequencies employing a cavity resonator external to the tube comprising an envelope, a cathode, a control grid, first and second high potential annular electrodes and a collecting electrode arranged in that order in the envelope, said first annular electrode having a given annular diameter, said envelope having a wall portion adjacent said first annular electrode' having a reentrant portion whose internal diameter is slightly smaller than the internal diameter of said the first annular electrode and tapers outwardly toward the second annular electrode, whereby the wall portion is struck throughout its surface by electrons emitted by said cathode.

References Cited in the file of this patent UNITED STATES PATENTS 2,253,080 Maslov Aug. 19, 1941 2,394,055 Hansen Feb. 5, 1946 2,545,073 De Vries Mar. 13, 1951 

